What are the limitations of running a PHP application on a CD, such as the inability to write to the CD during runtime?

When running a PHP application on a CD, one limitation is the inability to write to the CD during runtime. This means that any changes or updates to the application cannot be saved directly to the CD. To address this limitation, one solution is to use a writable storage location, such as a USB drive or external hard drive, to store any dynamic data or updates.

// Check if writable storage location is available
if (is_writable('/path/to/writable/location')) {
    // Save dynamic data or updates to the writable location
    file_put_contents('/path/to/writable/location/data.txt', 'Dynamic data or updates');
} else {
    echo 'Writable storage location is not available.';
}